KR100963472B1 - Metallic fuel rod in metal sheath including metallic fuel particles and a preparation method thereof - Google Patents

Abstract

The present invention relates to a metal fuel rod including a metal sheath encapsulated with metal fuel particles and a method for manufacturing the same. Specifically, the metal particles prepared by the spraying method are filled with nuclear fuel to reduce the generation of high-level nuclear waste and improve economic efficiency. The metal sheath filled with the metal fuel particles may be inserted into a coating tube to prepare a metal fuel rod that is prevented from chemical and mechanical interactions during fuel combustion, and the stability may be achieved using the fuel rod. It can provide a secured reactor.

Nuclear Fuel Particles, Sodium Metal Cooling Furnace, Uranium-Zirconium Alloys, Gas Spray, Centrifugal Spray, Vibration Filling, Metal Sheath

Description

Metallic fuel rod including a metal sheath encapsulated with metal fuel particles and a method for manufacturing the same

The present invention relates to a metal fuel rod comprising a metal sheath encapsulated with metal fuel particles and a method of manufacturing the same.

The world's energy demand is expected to increase more than twice in 2050 and more than three times by 2100. The future energy supply and demand problem can be solved by simply increasing the amount of electricity generated by the existing power generation system that is operating today. It requires clean, safe, economical and reliable power generation.

Nuclear power now operates 441 reactors in 31 countries around the world, accounting for about 17% of the total electricity production, and supplies nearly 1 billion people. Some developed countries, including France, rely on nuclear for more than half of their total electricity supply, and 32 other countries are currently operating, constructing or planning nuclear reactors. Globally, nuclear power produces electricity without releasing greenhouse gases into the atmosphere in a reliable and environmentally friendly manner and also has an excellent record of operation. Thus, nuclear power generation is the closest to a clean, safe, economical and reliable power generation method. In addition, the role of nuclear power in future energy supply is becoming more important due to concerns about soaring oil prices, climate change, air pollution, energy security and limited resource reserves.

The Office of Nuclear Energy, Science and Technology of the US Department of Energy (DOE) said that based on the need for nuclear power, the government, for its next generation nuclear energy system named "Generation IV," A global consultation forum was formed, covering industry and research institutes. The fourth-generation reactor is a new concept of innovation that will be developed with the goal of deploying globally around 2030 when most of the nuclear power plants in operation around the world are either retired or shut down. Candidate groups for the fourth generation reactor are as follows.

1.Very High Temperature Reactor (VHTR)

The ultra-high temperature gas cooler is the furnace closest to construction among the candidate reactors and is called NGNP. The ultra-high temperature gas cooler is planned to be built in the Idaho National Laboratory (INL), a full-scale demonstration that can be used for power and hydrogen production and produce hydrogen at low cost from 2016 to 2017. The coolant is helium, the moderator is graphite, a thermal neutron spectral reactor with an outlet temperature above 1000 ° C, and the reactor heat output is 400-600 MWt.

2. Lead-Cooled Fast Reactor (LFR)

The lead in the lead cooling fast reactor development program is to develop a relatively small (10-100 MWe) lead or lead-bismuth cooling fast growing reactor to be ready for commercialization by 2025 through demonstration. LFR is considered a turnkey nuclear power plant in a closed fuel cycle with a cassette core or sealed replacement reactor module with an ultra-long cycle of 10-30 years.

3. Gas-Cooled Fast Reactor (GFR)

Gas-cooled fast reactors are reactors with fast neutrons and circulating fuel cycles that allow for complete recycling of actinide on-site. Thermal neutron helium coolers, such as GT-MHR (Gas-Turbine Modular Helium Reactor) and PBMR (Pebble Bed Modular Reactor), can produce high-efficiency heat, hydrogen and process heat with high efficiency. The gas-cooled fast reactor uses a direct-cycle helium turbine with an efficiency of 42% at 850 ° C.

4. Supercritical Water-Cooled Reactor (SCWR)

Supercritical Water Cooling Furnace is a supercritical reactor operated at high temperature and high pressure which is thermodynamically above water critical point (374 ℃, 22.1MPa) based on the conventional light water reactor and supercritical thermal boiler technology. With about 45% higher efficiency atoms, low cost power generation costs can be realized.

5. Molten-Salt Cooled Reactor (MSR)

MSR has a thermal neutron spectral cyclic fuel cycle and is a reactor for the production of electricity and hydrogen, efficient combustion of plutonium and minor actinides, and the production of fissile fuel. MSR's fuel is sodium, zirconium and uranium fluoride. This is a combined circulating liquid mixture. Molten salt fuel flows through the graphite core channel and generates a thermal neutron spectrum.

6. Sodium-Cooled Fast Reactor (SFR)

The Sodium Cooling Express is a liquid metal reactor that uses sodium (Na) as a coolant, and has a fast neutron spectral cycle fuel cycle and a metal (uranium-plutonium-minor actinide-zirconium) in the actinide recycling cycle. ) Fuel or MOX (uranium-plutonium oxide) fuel may be used. Furthermore, the output of the sodium cooling fastway can be developed in various sizes ranging from several hundred MWe class to 1500-1700 MWe modular. In particular, the sodium cooling expressway can utilize uranium resources more than 60 times by repeatedly recycling fuels, and dramatically reduce the amount of radioactive waste.

Among the nuclear reactors, Korea is participating in the research of ultra high temperature gas cooling furnace, gas cooling high speed furnace, supercritical water cooling furnace and sodium cooling high speed furnace.

In particular, sodium cooling high-speed reactors have invested about $ 50 billion in development costs over the last 50 years and are the most commercially available technologies with 300 reactors and years of operation.

The metal fuel rod for sodium cooling high speed furnace is manufactured in the form of a rod having a diameter of 4 to 7 mm by a conventional injection casting method. In the manufacture of metal fuel cores by the injection casting method, the molten uranium alloy melted in the crucible is injected into a quartz tube mold to coagulate, and the fuel tube is recovered by breaking and dismantling the quartz tube mold. A large amount of quartz tube separated and dismantled from the nuclear fuel core is generated in a large amount in the casting process and is treated as a radioactive waste, which is not easy to treat.

In addition, the uranium alloy molten metal is sucked from the crucible into the quartz tube mold, and the remaining residue solidifies in the crucible to generate a large amount of heel. In the process of injection of molten metal into the mold during decompression molding and the separation of the crucible and the mold, a large number of metal fuel core failures occurred due to defects or imperfections in shape or dimensions, resulting in a very poor yield rate of 50% compared to the charged amount. There is. Furthermore, when casting by the pressure reduction casting method, the inside of the quartz tube mold is made in a vacuum state, and the pressure reducing furnace is pressurized, that is, a pressure difference is generated from the outside of the quartz tube mold so that the molten uranium is sucked into the mold by the pressure difference. . Therefore, it is necessary to dissolve the uranium alloy in vacuum. In this case, Am, a long-life extinction-treated nuclide extracted from spent nuclear fuel, must be collected during dissolution casting and converted to nuclide, but there is a problem that most of them evaporate due to strong volatility.

The nuclear fuel is rod-shaped with a diameter of 4-7mm, and the center of the nuclear fuel is at a high temperature of 650 ° C or higher.As a result of temperature difference between the outer circumference and the nuclear fuel of 100 ° C or higher, redistribution movement of zirconium, minor actinide, and rare earth occurs. Nuclear fuel composition varies depending on the part within and shows the difference in combustion behavior. In particular, swelling that occurs suddenly at the beginning of combustion causes contact with the coating material, and rare earth metals such as scandium, yttrium, lanthanum, cerium praseodynium, and actinium-based elements such as neodymium, neptunium, plutonium, and americium quium Chemically and physically react with each other to induce chemical / fuel / cladding chemical interactions (FCCI) and mechanical interactions (FCMI), which can damage cladding and shorten fuel life. There is a problem of increasing fuel recycle costs.

Due to these problems, the sodium cooling highway has been proven technically feasible through research and development, but it is most required to solve the safety problem due to unfavorable economics and a series of accidents.

Accordingly, the present inventors can reduce the generation of high-level nuclear waste and improve the economic efficiency by filling the metal particles prepared by the spraying method with nuclear fuel, and inserting a metal sheath filled with the metal fuel particles into the cladding to provide fuel / coating chemistry during fuel combustion. The present invention has been completed by developing a metal nuclear fuel rod that has safety by preventing red and mechanical interactions.

It is an object of the present invention to provide a metal fuel rod comprising a metal sheath encapsulated with metal fuel particles.

Another object of the present invention is to provide a method for producing a metal fuel rod comprising a metal sheath enclosed with metal fuel particles.

In order to achieve the above object, the present invention provides a metal fuel rod comprising a metal sheath encapsulated metal fuel particles of different sizes.

Furthermore, the present invention provides a method for producing the metal nuclear fuel rods.

According to the present invention, it is possible to reduce the generation of high-level nuclear waste and to improve the economic efficiency by filling the metal particles prepared by the spraying method with nuclear fuel, and inserting the metal sheath filled with the metal fuel particles into the cladding tube for fuel / coating tube during nuclear fuel combustion. In addition to manufacturing a metal fuel rod prevented from chemical and mechanical interactions, the nuclear fuel rod may be used to provide a nuclear reactor having stability.

Hereinafter, the present invention will be described in detail.

The present invention provides a metal fuel rod comprising a metallic sheath and liquid sodium comprising coarse metal fuel particles and fine metal fuel particles in a cladding tube (see FIG. 1).

Metallic fuel particles according to the present invention are uranium and zirconium alloys; Alloys of uranium, zirconium and rare earth elements; And an alloy of uranium, zirconium, rare earth-based elements, and actinium-based elements, and is used as a nuclear fuel for sodium-cooled fast reactor (SFR). Since the alloy can be dissolved and powdered in an inert atmosphere, rare earths and actinium-based elements having high volatility are not evaporated, and thus the alloy can be used as a metal fuel capable of long-life nuclide extinction in a sodium-cooled fast reactor. The rare earth element may be scandium, yttrium, lanthanum, cerium or praseodynium, and the actinium-based element may be neodymium, neptunium, plutonium, americium or querium.

Coarse metal fuel particles according to the present invention is preferably 0.1 to 1 mm. In this case, when the coarse metal nuclear fuel particles exceed 1 mm, the particle filling density is lowered, and when the coarse metal nuclear fuel particles are smaller than 0.1 mm, the pores to which the fine particles are charged are reduced. Further, the fine metal fuel particles are preferably 0.01 to 0.1 mm. If the fine metal fuel particles are 0.01 mm, handling is not easy.

The particle filling density of the fuel particles in the metal sheath included in the metal fuel rod according to the present invention is preferably 70 to 80%. When the particle density exceeds 80%, the nuclear fuel swells rapidly at the initial stage of irradiation to cause mechanical deformation of the nuclear fuel rod, and if it is less than 70%, there is a problem of low fuel efficiency.

Furthermore, the diameter ratio of the coarse metal fuel particles and the fine metal fuel particles is 5: 1 to 15: 1, and the mixing ratio of the coarse metal fuel and the fine metal fuel particles is 1: 1 to 1: 9. If the diameter ratio and the mixing ratio of the coarse metal fuel particles and the fine metal fuel particles are out of the above range, there is a problem that the particle filling density of 70 to 80% is out of range.

The metal sheath included in the metal fuel rod according to the present invention includes metal fuel particles, thereby restricting the swelling of the nuclear fuel by adding a binding force to the dimensional change in the radial direction during irradiation, and preventing direct contact between the cladding tube and the fuel. Chemically and mechanically stable metal fuel rods can be produced by preventing chemical reactions to reduce the fuel / cladding chemical interaction (FCCI) and mechanical interactions. In this case, the metal sheath may be made of zirconium, chromium, vanadium, molybdenum, niobium or titanium.

In addition, the cladding tube of the metal nuclear fuel rod according to the present invention may use stainless steel.

The present invention also provides a method for preparing and classifying metal fuel particles (step 1);

Vibration filling the coarse metal nuclear fuel particles classified in step 1 into the metal sheath (step 2);

Inserting the metal sheath of step 2 filled with coarse metal fuel particles into the sheath by vibrating and filling the fine metal fuel particles with fine metal fuel particles (step 3);

Loading the pin-shaped solid sodium into the cladding tube of step 3, dissolving by heating in a vacuum state, and cooling the solid sodium into the nuclear fuel rod by injecting an inert gas (step 4);

Preparing a nuclear fuel rod by forming and welding a vacuum or inert gas atmosphere inside the metal fuel particles and the filled sheath (step 5); And

It provides a method of manufacturing a metal fuel rod comprising the step (step 6) of bonding the sodium charged in the step 4 to the nuclear fuel core while heating the nuclear fuel beam of step 5 (see Fig. 2).

Hereinafter, the present invention will be described in detail step by step.

The metal nuclear fuel particles of step 1 according to the present invention are uranium and zirconium alloy; Alloys of uranium, zirconium and rare earth elements; And alloys of uranium, zirconium, rare earth elements, and actinium-based elements.

In this case, the rare earth element is scandium, yttrium, lanthanum, cerium or praseodynium, and the actinium-based element is preferably neodymium, neptunium, plutonium, americium or querium.

In addition, the metal nuclear fuel particles of step 1 may be prepared by gas spraying or centrifugal spraying.

In the production of particles, the gas spray can be prepared by spraying a uranium-zirconium alloy dissolved in an inert atmosphere through a nozzle at a constant spraying gas pressure and then rapidly solidifying. The centrifugal spraying is performed by injecting the uranium-zirconium alloy dissolved in a crucible into an inert atmosphere. The molten metal is supplied to the rotating disk by tapping through a nozzle at and sprayed to prepare metal nuclear fuel particles.

The ratio of the coarse metal nuclear fuel particle diameter and the fine metal nuclear fuel particle diameter classified in step 1 may be performed to be 5: 1 to 15: 1. If the diameter ratio of the coarse metal fuel particles and the fine metal fuel particles is out of the range, there is a problem that the particle filling density of 70 to 80% is out of range. Furthermore, the coarse metal nuclear fuel particles are preferably 0.1 to 1 mm. If the fine metal fuel particles are less than 0.01 mm, handling is not easy.

Step 2 according to the present invention is a step of vibrating the coarse metal nuclear fuel particles classified in step 1 into the metal sheath.

The metal sheath-filled coarse metal nuclear fuel particles can be vibrated to form a dense stacked structure within the metal sheath. The vibration filling may be performed by placing a vibrating powder filling device on the bottom of the metal sheath and applying vibration. Furthermore, after the funnel is installed in the metal sheath, the metal fuel particles can be filled to prevent the metal fuel particles from being lost. At this time, the vibration is not particularly limited, but ultrasonic vibration is used, and the metal sheath is preferably made of zirconium.

Step 3 according to the present invention is a step of vibration-filling fine metal fuel particles in the metal sheath of step 2 filled with coarse metal fuel particles and inserting them into the cladding tube.

The fine metal fuel particles of step 3 may be filled in the same manner as the method of filling coarse metal fuel particles in step 2, and the coating tube is preferably made of stainless steel.

Step 4 according to the present invention is a step of loading the pin-shaped solid sodium in the cladding tube of step 3, heating and dissolving in a vacuum state, and then cooling the solid sodium in the nuclear fuel rod by injecting an inert gas.

In step 4, the solid sodium extruded in the form of pins is filled between the uniformly and densely stacked metal nuclear fuel particles in step 3, and heated and dissolved in a vacuum state so as not to generate impurities, and there is no side reaction. Cooling while supplying an inert gas. At this time, the heating is preferably heated to 150 ℃ ~ 250 ℃ using sodium settler (Na settler). If the heating exceeds 250 ℃ there is a problem that bubbles in sodium are generated, if less than 150 ℃ there is a problem of low fluidity, causing degassing and powder filling disorders.

Step 5 according to the present invention is the step of creating and welding a vacuum or inert gas atmosphere inside a metal tube filled with nuclear fuel particles and sodium.

The welding of step 5 according to the present invention is a step of sealing with a cover made of a material such as a cladding tube in a cladding tube filled with metal fuel particles and sodium. The welding is preferably performed by using a TIG method, laser welding or electron beam welding after closing the cover to discharge air remaining in the fuel internal space to form a vacuum atmosphere. At this time, the air remaining in the cladding tube is expanded during nuclear fuel combustion to deform the fuel rod.

Step 6 according to the invention is a step of binding sodium to the nuclear fuel core while heating the fuel rods.

Vibration-filled solid sodium in an inert atmosphere and heated to Melting step. The heating melts the solid sodium charged in step 4, so that the molten sodium penetrates into the liquid phase between the metal fuel particles to facilitate heat transfer. At this time, the heating is preferably heated to 400 ~ 600 ℃ using sodium setler. If the heating exceeds 600 ℃ there is a problem that bubbles in sodium are generated, if less than 4000 ℃ there is a problem that causes the fuel powder filling failure due to low fluidity.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are merely to illustrate the present invention, the content of the present invention is not limited by the following examples.

Example 1 Preparation of Metal Fuel Rod Encapsulated Metal Nuclear Fuel Particles

Step 1. Prepare and classify the metal fuel particles.

Purified 99.9% purity uranium lumps and purity 99.7% zirconium sponges were charged in a high-temperature ceramic crucible, and then vacuum-induced, followed by induction-melting at 1600 ° C to prepare molten metal fuel alloys. . The molten metal fuel alloy was centrifugally sprayed into a rotating disk having a diameter of 35 mm in an inert atmosphere at a rotational speed of 7,000 rpm to rapidly solidify metal fuel particles having a diameter of 1 mm or less (see FIG. 2).

The prepared metal fuel particles were classified into coarse metal fuel particles of 0.1 to 1 mm and fine metal fuel particles of 0.01 to 0.1 mm using a vibrating particle polarizer.

Step 2. Charging Coarse Metal Nuclear Fuel Particles in the Metal Sheath

 The vibration powder filling device was placed under the metal sheath formed of zirconium, and coarse fuel particles classified in step 1 were first charged while generating vibration by ultrasonic waves.

Step 3. Filling the fine metal fuel particles in the metal sheath and inserting the metal sheath into the sheath.

After the coarse fuel particles were charged, fine uranium-zirconium powders of 0.3 mm or less were filled between the coarse powders using a vibrating powder filling device. The metal varnish filled with the metal fuel particles was then inserted into a cladding tube made of stainless steel.

Step 4. Filling Sodium Filled Solid Sodium

The solid sodium is charged into the cladding tube between the metal fuel particles, the solid sodium is melted at 200 ° C. using a Na meltdown furnace in a vacuum of 1.0 × 10 ⁻² torr, and the inert gas is charged into the cladding tube and cooled. I was.

Step 5. Welding of Metal Fuel Particles and Filled Cladding Tubes

Closing the stainless steel cover on the top of the open cladding tube of step 5 and vacuuming the fuel inner space to extract air, the stainless steel lid was closed on the cladding tube and welded with an electron beam in a vacuum or inert atmosphere to prepare a nuclear fuel rod.

Step 6. Heat sodium and bond to fuel core

A vibrating filling device was placed underneath the sheath into which the metal sheath was inserted, solid sodium was charged into the sheath in an inert atmosphere, heated to 500 ° C. for 1.5 hours to dissolve, and bonded the liquid sodium between the stacked nuclear fuel particles. A vibrating filling device was placed underneath the sheath into which the metal sheath was inserted, solid sodium was charged into the sheath in an inert atmosphere and then heated to dissolve for 10 minutes at 500 ° C. to fill the liquid sodium between the stacked nuclear fuel particles.

Example 2 Fabrication of Metal Nuclear Fuel Rod Encapsulated Metal Nuclear Fuel Particles

In Step 1 of Example 1, except that the molten metal nuclear fuel alloy was sprayed with a spray gas pressure of 5 bar at a nozzle diameter of 2 mm in an inert atmosphere to prepare a rapidly solidified uranium-zirconium spherical powder particles having a diameter of 0.3 mm or less. Was carried out in the same manner as in Example 1 to prepare a nuclear fuel rod.

Comparative Example 1

Metallic Nuclear Fuel Cores Fabricated by Vacuum Casting

<Analysis>

1. Metallic Fuel Particles

The metal nuclear fuel particles prepared in Step 1 of Example 1 and the microstructure of the particles were measured in an electron scanning microscope and are shown in FIGS. 3 and 4.

As shown in Figure 3, the metal nuclear fuel particles according to the present invention was confirmed that the perfect spherical particles with a smooth surface at a diameter of 0.01 mm ~ 1 mm.

As shown in FIG. 4, the interior of the metal fuel particles according to the present invention was composed of a laminar structure, so that the nuclear fission generating gas can escape through a phase boundary.

1 is a conceptual diagram of a metal fuel rod according to the present invention;

2 is a method of manufacturing a metal fuel rod according to the present invention;

3 is an apparatus (a) for producing metal fuel particles and metal fuel particles according to the present invention; And

Figure 4 is a cross-sectional structure (a) and cross-sectional formula (b) of Comparative Example 1 of the metal nuclear fuel particles according to the present invention.

Claims (20)

A metal fuel rod comprising a metallic sheath and liquid sodium comprising coarse metal fuel particles and fine metal fuel particles in a cladding tube. The method of claim 1, wherein the metal fuel particles are uranium and zirconium alloy; Alloys of uranium, zirconium and rare earth elements; And uranium, zirconium, rare earth-based elements, and metal nuclear fuel rods, characterized in that they are alloys of actinium-based elements. The metal fuel rod of claim 2, wherein the rare earth element is scandium, yttrium, lanthanum, cerium, or praseodynium, and the actinium-based element is neodymium, neptunium, plutonium, americium, or querium. The metal fuel rod of claim 1, wherein the coarse metal nuclear fuel particles are 0.1 to 1 mm in diameter. The metal fuel rod according to claim 1, wherein the fine metal fuel particles are 0.01 to 0.1 mm in diameter. The metal nuclear fuel rod according to claim 1, wherein the particle filling density of the nuclear fuel particles in the metal sheath is 70 to 80%. The metal fuel rod according to claim 1, wherein a diameter ratio of the coarse metal fuel particles to the fine metal fuel particles is 5: 1 to 15: 1. The metal fuel rod according to claim 1, wherein the mixing ratio of the coarse metal fuel and the fine metal fuel particles is 1: 1 to 1: 9. The metal nuclear fuel rod according to claim 1, wherein the metal sheath comprises at least one selected from the group consisting of zirconium, chromium, molybdenum, tantalum, tungsten, vanadium and titanium. The metal nuclear fuel rod of claim 1, wherein the cladding tube is stainless steel. Preparing and classifying metal fuel particles (step 1); Vibration filling the coarse metal nuclear fuel particles classified in step 1 into the metal sheath (step 2); Inserting the metal sheath of step 2 filled with coarse metal fuel particles into the sheath by vibrating and filling the fine metal fuel particles with fine metal fuel particles (step 3); Loading the pin-shaped solid sodium into the cladding tube of step 3, dissolving by heating in a vacuum state, and cooling the solid sodium into the nuclear fuel rod by injecting an inert gas (step 4); Preparing a nuclear fuel rod by forming and welding a vacuum or inert gas atmosphere inside the metal fuel particles and the filled sheath (step 5); And Bonding the sodium charged in step 4 to the nuclear fuel core while heating the fuel rod of step 5 (step 6). 12. The method of claim 11, wherein the metal nuclear fuel particles of step 1 are uranium and zirconium alloy; Alloys of uranium, zirconium and rare earth elements; And uranium, zirconium, rare earth-based elements, and alloys of actinium-based elements. The method of claim 12, wherein the rare earth-based element is scandium, yttrium, lanthanum, cerium, or praseodynium, and the actinium-based element is neodymium, neptunium, plutonium, americium, or querium. 12. The method of claim 11, wherein the metal nuclear fuel particles of step 1 are produced by gas atomization or centrifugal atomization. The method of claim 11, wherein the classification of the metal fuel particles prepared in step 1 is characterized in that the ratio of the coarse metal fuel particle diameter and the fine metal fuel particle diameter so that the ratio of 5: 1 to 15: 1 of the metal fuel rod Manufacturing method. 16. The method of claim 15, wherein the coarse metal nuclear fuel particles are 0.1 to 1 mm in size. 16. The method of claim 15, wherein the fine metal fuel particles are 0.01 to 0.1 mm in size. The method of claim 11, wherein the heating of the step 4 is a method of producing a metal fuel rod, characterized in that 150 ℃ ~ 250 ℃. 12. The method of claim 11, wherein the welding of step 5 is TIG welding, electron beam welding, or laser beam welding. 12. The method of claim 11, wherein the heating of step 6 is 400 ℃ ~ 600 ℃.

Images